The human placenta enjoys immunity from host rejection for unknown reasons, although there is evidence that chorionic gonadotropin may play a role in immunosuppression at the placental size. lg, however, has been reported along the trophoblastic membrane and, in our studies, along the fetal endothelium (Fed. Proc. 40:578, 1981). The purpose of this study is to homogenize whole placentas and to characterize the Ig removed by acid elution.